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Post by Godzillasaurus on Dec 19, 2013 22:52:03 GMT 5
It would have been most resistant in the area posterior to the diastema region. So when spinosaurus bit the neck or back of a large terrestrial animal, it would have needed to clamp down using that area instead of the diastema, as it would have the least chance of breaking (and actually appears to have been much stronger than many claim, based on its overall robusticity). Clamping down on such an animal with just the premaxilla area would be very risky for spinosaurus (given its rostrum's overall build in that area, which was clearly very specialized for piscivory), so the rostrum as a whole was not necessarily resistant, but rather the region posterior to the red line (in Figure 5) and/or general premaxilla area.
Spinosaurus would have likely not used only the tip of its snout when taking down large terrestrial animals (given its very specialized and gracile shape and the fact that the animal's bite force would be VERY subtle in that area), but would rather clamp down with its more resistant central region to prevent breaking. In this case, the sheer combination of theoretical violent vertical shaking and the theropod's long maxillary teeth in that area would be very deadly in terms of spinal damage (you know, as spinosaurus lacked an exceptionally powerful bite).
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Post by theropod on Dec 20, 2013 2:49:51 GMT 5
It's rather that there's no proper reason to presume it would have used the premaxilla to deliver killing bites. That does not even seem to be the role of the premaxillary dentition in other theropods, which do not have such a specialized gripping adaption. in this region.
So that this region is less robust is not really of great importance to the strenght of the structure as a whole--it was likely considerably stronger posterior to it, in the largest part of the snout, and thus also in general. How much exactly we cannot tell.
Note also that being so much larger we should expect it to be more robust than crocodilians like Gavialis, Tomistoma or Mecistops, so if it is (in the case of MNHM this seems to be the case) it's not a surprise.
As with Giganotosaurus, I'll wager we should assume 2t is not the posterior bite force for Spinosaurus. Sadly how well the rostral robusticity correlates with it between spinosaurs and crocodilians and how much the former relied on it is a big unknown. Some testing on the penetration ability, resistance etc. of their teeth would be very useful.
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Post by Godzillasaurus on Dec 20, 2013 3:03:54 GMT 5
This is why I believe that they should have used more than just this area in the study.
Larger as in what? Wider? Deeper? Because the largest spinosaurus specimens (such as MNHM, as you said, but also the Spinosaurus genera in general) are characterized by particularly robust "post-premaxillary" rostra, and comparisons between them and those of the genera that you listed actually show that it was reasonably broader at the center of the rostrum and more heavily-built in spinosaurus. And what is not a surprise, exactly?
We do know that spinosaurus' dentition was at least very well designed and structured for piercing into the hides of tough-skinned animals, fundamentally (they were quite long, relatively slender in shape, and were generally sharply pointed as well, especially at the tip of the snout and the middle of the maxilla). They were also quite sturdy as well, as evidenced by their spike-like structure (although still slender as well, and certainly not adapted for crushing), so resistance in their case was also not likely an issue. They were designed mainly for hunting and catching fish, as evidenced by their well-suited structure for rather deep penetration and effective grasping. But yes, I feel that more tests in this realm need to be put into place.
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Post by theropod on Dec 20, 2013 18:22:01 GMT 5
I meant that Spinosaurus was simply larger in overall body and skull size, and such larger animals tend to have more robust proportions.
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Post by theropod on Dec 22, 2013 0:24:35 GMT 5
Crocodilians are among the animals with the highest bite forces that ever lived, also, and especially, relative to their body sizes. Even Gavialis and Tomistoma have respectable power in their jaws. If Spinosaurus supposedly vastly outperforms them (which I doubt) in skull strenght, why should it not also do so in bite force?
Piscivorous or not (extant crocodilians are too!), your set of analogies does not make sense. Especially as a piscivore, it would have needed to excert and absorb enough force to drag a struggling fish of decent size. Even more so in your "vertical shaking" scenario.
Nobody is arguing it would have or need an "EXCEPTIONALLY powerful bite", that it would need it (as I explained to you there's a bit difference between reliance on sheer mechanical damage inflicted by a bite, reliance on crushing power, and reliance on classic, perpendicular biting with the aid of precision), that it's jaws were not built for piscivory/to reduce drag in the water, or that it killed by extensive crushing like some of the analogies you undoubtedly have in mind.
but what you write simply seems very repititive and almost contradictory. You go on from arguing about how impressive the strenght of it's rostrum must have been, to claiming it to have been too weak for forceful biting.
it's rostrum was relatively deepened compared to crocodilians, relatively shallow & narrow compared to other theropods, relatively wide compared to baryonychines. It's teeth were pretty long comparedc to both most crocodiles and baryonychines, and show caniniform hypertrophy in the anterior parts of the toothrow, of course primarily an adaption for a firm grip in these regions.
What do you want to make of that? Decide!
I choose to interpret it the way I already summarized, that it was primarily a specialized predator of small prey and fish, and that when it killed big(ger) game, it would have gone for the neck witht he aim of puncturing the vital structures there with the application of an intermediate amount of bite force over a pointed, slender tooth.
I did and would not say that. I would now suggest (based on direct comparison and use of analogies in other spinosaurs and crocodilians) that most likely its bite force would have been roughly comparable, but used in a very different manner, and most likely to a lesser effect on large prey.
I'd say it may have excerted roughly 2t at the large postdiastemal teeth (vs 2-3t along the toothrow in Carcharodontosaurus and Giganotosaurus).
Whether that holds true this way is of course very hard to say due to our lack of complete crania or complete testing on them. But it's probably a good guess for now.
Again, I never talked about crushing), but your reasoning is inconsistent. If it was strong enough to sustain a crushing force, and the teeth were too, it could have been used for crushing. Now I am not the one who suggests it was...
Have you directly compared them? Large specimens of Mecistops can have really robust skulls, and you may recall I compared it to Sarcosuchus on one occasion (remember the image I posted then!). Any difference we see is very likely just size-dependant.
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Post by Godzillasaurus on Dec 22, 2013 3:51:49 GMT 5
SoÂ… Now you are disagreeing with the fact that spinosaurus would have likely outperformed those genera if the whole rostrum was used? Didn't you agree on that before? I quote you: "Note also that being so much larger we should expect it to be more robust than crocodilians like Gavialis, Tomistoma or Mecistops, so if it is (in the case of MNHM this seems to be the case) it's not a surprise."
High biting force is not a necessity for a piscivorous animal like spinosaurus. Now, it certainly had a relatively powerful bite, don't get me wrong. But certainly not a monstrously powerful one. Not much has been studied on its bite force, so I really cannot say much in how well it did compared to those genera.
The force here rather relies on the strength of the animal's neck and its ability to effectively maintain a stable grip, not the actual impact of the bite itself. This animal was not tyrannosaurus; it did not kill with impressive direct (biting) force-related tactics.
The rostrum would have been strong in its resistance to force (as, again, it was very heavily built in the centralmost region, where general resistance would naturally be much higher than the premaxilla due to its less gracile morphology) not necessarily being excessively strong in its delivery of force (it was not especially wide). When I am talking about "forceful biting" I am not talking about its ability (or inability thereof) to exert the same kind of biting power as seen in animals like tyrannosaurus. Of course it had a powerful bite in its own regard, but certainly nowhere near such crushing capabilities. Unless I am misunderstanding you, which is probably the case. I am just having trouble comprehending the "classical perpendicular biting" idea, as spinosaurus was simply not designed for doing this (don't get me wrong, its teeth were more than capable of impaling deeply into the hide of a prey animal, but any actual fatal damage would most likely be attributed to another factor. The teeth would be complimentary to the damage done, as they were designed for gripping, fundamentally)
Haha! I am making this too confusing, aren't I? Umm, let's see here.
All of those are characteristics of spinosaurus: generally deep rostrum compared to modern crocodilians but quite shallow compared to most groups of macro predatory theropods (like carnosaurs, tyrannosaurids, megalosaurids, and ceratosaurs for example. In spinosaurus, the increased depth instead appears to be for resistance purposes in gripping), relatively narrow rostrum (although much wider in relation to depth than in animals like allosauroids or megalosaurids, implying more balanced strength aiding predation on large fish) that were still quite dense and heavily-constructed, and finally long and specialized dentition that was perfectly designed to pierce deeply (yet, being a primarily piscivorous animal, they were not designed for killing. Although they COULD be used for killing, under the right circumstances) and very robust and sturdy as well.Â
This isn't opinion based, so I really cannot "decide" what to make of it, unfortunately.Â
I agree with all of that EXCEPT for the part about the bite force. I need some more insight on that part, as I said earlier.
Its rostral and mandibular robusticity and density is what makes them strong. This does not correlate with its actual bite force but rather its ability to withstand such pressures. I have no doubt in my mind that spinosaurus was capable of doing so, it is just that its diet and morphology suggested that it did not require such a powerful (crushing) bite. Its teeth were designed very specifically to pierce deeply and retain a stable grip on large fish, but that does not imply that it had such a powerful bite but rather the direct opposite. I'm sorry for making this hard on you with all of this "confusion", I am probably just misunderstanding you, that's all.
Large specimens of spinosaurus (such as the Chibi, Japan one) have particularly robust post-premaxillary rostra as well. So yes, the differences do appear to have been size dependent, considering how that specimen appears to have been quite large in general (unsure how large exactly). That is on me, as I didn't put that into consideration when I compared them. My bad
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Post by theropod on Dec 22, 2013 20:13:34 GMT 5
I was not saying Spinosaurus snout was more robust than Mecistops, you were the one who continuously repeats that. I was reminding you that if it is (at least it's obviously more robust than the former two in lateral aspect) the case it's not because it shook it's prey vigorously like a Saltie, but rahter because being bigger it would have to compensate for the effects of scaling.
It's needed just as much as the capability to absorb forces induced on it by it's struggling prey. And if an animal is shaking something, it's bite force has to be strong enough to keep it's mouth shut. Your scenario would likely require a far greater bite force than mine.
and what does an animal need to "effectively maintain a stable grip"? The necessary power in the musculature powering that very grip.
There's no difference here. Either a structure can bear the stress, or it cannot.
There's no physical difference between the stress caused by a classic bite and the stress caused by a non-bite-related factor in the same plane as long as it's of the same magnitude.
Ok, I'll resume it again.
-strong bite force, strong enough for impaling deeply with its teeth (NOT massive crushing power over an extensive area)
-sufficient resistance in the rostrum and mandible
-->least risky and most logical way it could have used it's jaws in killing
I propose it was that very puncturing adaption it could have used in a secondary function to dispatch larger prey, instead of some other, more unlikely tactic.
All it's physiological capabilities are fully sufficient for that, and if they weren't, then they'd be even less suited for grabbing a large fish or executing some "vertical shake" or tearing motion.
My problem with this is merely that your alternate explanation would require even more reliance on brute force, including jaw-adductor-strenght. So why assume that instead, if what we see can be explained much more easily and conservatively (without the need for monstrously strong crushing bites in piscivores)?
You see, I do not propose it killed in any way like a tyrannosaurine, but neither like a crocodile or some strange crocodile-allosaur-composite. I presume it killed most similar to a feline (albeit it certainly did not kill prey of such large relative size) or a raptor, by precise puncturing, not extensive crushing. This also requires far less force to be excerted, and accordingly poses smaller stress on the skull.
again, that specimen is not in Japan but in Milano. The japanese mount is merely a composite of replica.
I was already talking about that one. The NHMUK rostrum is less robust, bust so was the specimen of Mecistops cataphractus in the Cuff & Rayfield paper.
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Post by Godzillasaurus on Dec 22, 2013 20:53:52 GMT 5
Ah, I see. As I said, that was a mistake that I had previously made; I didn't think about the actual size or age of the animal first hand.
In a way, yes. But that is only if the ability to keep your mouth shut and retain a stable grip is one of the same with the actual impact force itself.
Again, only if the actual bite force is the same thing as the direct force itself. In this case, this would apply to all animals really. I had always thought that the force to "hold on" to things is very different from the initial bite force.
Ah, I see. However, the main problem that I have with this is that spinosaurus was again structured to have been adapted for gripping. Its snout was designed to withstand the pressures experienced in the predation and capturing of large fish, so naturally it would have to be strong. But it simply was poorly-adapted for crushing, as it not only did it lack a snout morphology that suggested it (such as a generally wider snout and differently-shaped teeth), but its ecology simply did not require it.
Ok, you got me!
I see
I'm bad with specimens and that sort of stuff.
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Post by theropod on Dec 22, 2013 21:10:32 GMT 5
I don't think there's any Spinosaurus specimen that's housed in Japan. The most famous ones are the destroyed holotype, which was in Munich, and the huge rostrum described by Dal Sasso.
It depends how you are holding on to something.
If you are MERELY pulling posteriorly or the prey is trying to pull free in anterior direction, and your teeth are built as to not release something in such a case (like eg a snake) your bite force is not that important. But if you lift something, the whole weight is loaded on your mandible. The same applies to the event of a vertical shaking movement (but the force will be even greater due to the accelleration), and lateral shaking (aside from great stress on the skull) also requires great amounts of force to avoid letting the prey slip from the jaws.
Some degree of bite force is of course necessary for holding, at least with straight teeth, besides teeth that are suited for it. It is both crucial that the teeth remain stuck firmly in the prey along their long axis (bite force), and that they do not tear themselves free (reduced tooth sharpness, ideally by conical shape).
Now, of course the bite force does not have to be monstrous in order to effectively grip something, because often the animal that is gripped is either smaller (like a fish) or does not have to be fully controlled, just somewhat stabilised to faciliate maneuvering (like another large dinosaur that's being fought). But some degree of it is necessarily needed, and that alone would likely be sufficient to also deal dangerous puncture wounds. If we assume the prey was dispatched by shaking, that'd definitely require a greater amount of force and resistance.
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Post by Godzillasaurus on Dec 22, 2013 21:21:54 GMT 5
Quote: If you are MERELY pulling posteriorly or the prey is trying to pull free in anterior direction, and your teeth are built as to not release something in such a case (like eg a snake) your bite force is not that important. But if you lift something, the whole weight is loaded on your mandible.
Well obviously this does not appear to be much of a problem for spinosaurus. Given the fact that it was a primarily ichthyophagous creature and possessed the general and expected morphology of one, it would have likely killed mostly by picking up a large fish. So this is where my theories about the creature's stresses in predation come from; being designed for gripping large fish as opposed to killing through the use of ripping, we would expect predation to be relatively high in terms of stress experienced.
Quote: But some degree of it is necessarily needed, and that alone would likely be sufficient to also deal dangerous puncture wounds.
Spinosaurus, aside from the entire gripping factor of it, would simply not require a necessarily very powerful bite to effectively create deadly puncture wounds. Unlike animals like tyrannosaurus and deinosuchus (for example) respectively, spinosaurus' teeth were quite sharp and elongate and were in fact perfectly designed for piercing deeply without much driving force (of course, its bite force was still moderate, just not monstrous as we see in those two genera). This definitely correlates with its snout shape, as it is to be expected that its snout would be strong enough for gripping large animals which is just what its teeth were designed for.
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Post by creature386 on Dec 23, 2013 0:04:25 GMT 5
I don't think there's any Spinosaurus specimen that's housed in Japan. The most famous ones are the destroyed holotype, which was in Munich, and the huge rostrum described by Dal Sasso. There is no specimen in Japan, but there is this reconstruction:  It isn't meant to represent a particular specimen, this is just a (15 meter long) Spinosaurus reconstruction, based on all we know about it. Source (not for the image, for the information, the image is from wiki): www.gigapan.com/gigapans/99633 |
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Post by theropod on Dec 23, 2013 3:32:55 GMT 5
Even tough I'll wager it isn't particularly accurate, I'd really love to see the japanese mount in person!
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Post by theropod on Mar 22, 2014 20:20:23 GMT 5
qilong.deviantart.com/art/Tyrannosaurus-Snouts-In-Section-441109879www.youtube.com/watch?v=DqexuSKikSw&fmt=22www.youtube.com/watch?v=aE2EdnR4300www.youtube.com/watch?v=4HApj9cxFYIwww.youtube.com/watch?v=CbRiF2RqWZ4These are of interest regarding the differences in cranial pneumatisation. By comparison, here’s the Ct-scan of Spinosaurus’ snout shown in Planet Dinosaur:  ©BBC (Planet Dinosaur) At its posteriormost extent, the Spinosaurus rostrum has a pneumatisation index of 23.0%, compared to ~50.9% in the mid-rostrum of T. rex specimen AMNH 5027. In other words, there’s more than 60% more bone in a Spinosaurus rostrum’s cross-section than there is in a T. rex snout. Given that the PD-CT is the actual thing, this is proof for what we presumed earlier, Spinosaurus’ rostrum is thin but compact. That gives the structure a certain degree of robusticity, especially with regard to local failure of material that would be an issue especially with torsional forces. However due to the configuration of the material it likely wouldn’t be as resistant to bending or as effective for applying force as other, deeper theropod rostra, because this makes it less rigid. Looking at those long teeth, they probably did not require that much resistance and force in order to be apt at gripping.
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Post by Godzillasaurus on Mar 25, 2014 23:44:27 GMT 5
Quote: However due to the configuration of the material it likely wouldn’t be as resistant to bending or as effective for applying force as other, deeper theropod rostra.
-This makes perfect sense actually when regarding the creature's dentition morphology/arrangement in comparison to that of more typical terrestrial-hunting theropods. It all corresponds greatly with its diet of mainly fish
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Post by theropod on Mar 27, 2014 1:51:51 GMT 5
Especially, that makes sense in combination with the dentary, which is exceptionally deep, and would have made the mandible overally wider than the rostrum, but at the same time relatively thin, i.e. not nearly as solid as the corresponding upper jaw, albeit bigger in dimensions.
That’s the part that would have to resist bending more so than the rostrum, given the animal snatched fish and lifted or pulled them out of the water from above.
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